/Engine/Source/Runtime/Online/HTTP/Public/Interfaces/IHttpRequest.h
Sets optional header info. SetHeader for a given HeaderName will overwrite any previous values Use AppendToHeader to append more values for the same header Content-Length is the only header set for you. Required headers depends on the request itself. Eg. "multipart/form-data" needed for a form post
void SetHeader ( const [FString](API\Runtime\Core\Containers\FString) & HeaderName, const [FString](API\Runtime\Core\Containers\FString) & HeaderValue )